/*
 * jdsample.c
 *
 * Copyright (C) 1991-1994, Thomas G. Lane.
 * This file is part of the Independent JPEG Group's software.
 * For conditions of distribution and use, see the accompanying README file.
 *
 * This file contains upsampling routines.
 *
 * Upsampling input data is counted in "row groups".  A row group
 * is defined to be (v_samp_factor * DCT_scaled_size / min_DCT_scaled_size)
 * sample rows of each component.  Upsampling will normally produce
 * max_v_samp_factor pixel rows from each row group (but this could vary
 * if the upsampler is applying a scale factor of its own).
 *
 * An excellent reference for image resampling is
 *   Digital Image Warping, George Wolberg, 1990.
 *   Pub. by IEEE Computer Society Press, Los Alamitos, CA. ISBN 0-8186-8944-7.
 */

#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"


/* Pointer to routine to upsample a single component */
typedef         JMETHOD(void, upsample1_ptr,
						(j_decompress_ptr cinfo, jpeg_component_info * compptr,
						 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr));

/* Private subobject */

typedef struct
{
	struct jpeg_upsampler pub;	/* public fields */

	/* Color conversion buffer.  When using separate upsampling and color
	 * conversion steps, this buffer holds one upsampled row group until it
	 * has been color converted and output.
	 * Note: we do not allocate any storage for component(s) which are full-size,
	 * ie do not need rescaling.  The corresponding entry of color_buf[] is
	 * simply set to point to the input data array, thereby avoiding copying.
	 */
	JSAMPARRAY      color_buf[MAX_COMPONENTS];

	/* Per-component upsampling method pointers */
	upsample1_ptr   methods[MAX_COMPONENTS];

	int             next_row_out;	/* counts rows emitted from color_buf */
	JDIMENSION      rows_to_go;	/* counts rows remaining in image */

	/* Height of an input row group for each component. */
	int             rowgroup_height[MAX_COMPONENTS];

	/* These arrays save pixel expansion factors so that int_expand need not
	 * recompute them each time.  They are unused for other upsampling methods.
	 */
	UINT8           h_expand[MAX_COMPONENTS];
	UINT8           v_expand[MAX_COMPONENTS];
} my_upsampler;

typedef my_upsampler *my_upsample_ptr;


/*
 * Initialize for an upsampling pass.
 */

METHODDEF void start_pass_upsample(j_decompress_ptr cinfo)
{
	my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;

	/* Mark the conversion buffer empty */
	upsample->next_row_out = cinfo->max_v_samp_factor;
	/* Initialize total-height counter for detecting bottom of image */
	upsample->rows_to_go = cinfo->output_height;
}


/*
 * Control routine to do upsampling (and color conversion).
 *
 * In this version we upsample each component independently.
 * We upsample one row group into the conversion buffer, then apply
 * color conversion a row at a time.
 */

METHODDEF void
sep_upsample(j_decompress_ptr cinfo,
			 JSAMPIMAGE input_buf, JDIMENSION * in_row_group_ctr,
			 JDIMENSION in_row_groups_avail, JSAMPARRAY output_buf, JDIMENSION * out_row_ctr, JDIMENSION out_rows_avail)
{
	my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
	int             ci;
	jpeg_component_info *compptr;
	JDIMENSION      num_rows;

	/* Fill the conversion buffer, if it's empty */
	if(upsample->next_row_out >= cinfo->max_v_samp_factor)
	{
		for(ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; ci++, compptr++)
		{
			/* Invoke per-component upsample method.  Notice we pass a POINTER
			 * to color_buf[ci], so that fullsize_upsample can change it.
			 */
			(*upsample->methods[ci]) (cinfo, compptr,
									  input_buf[ci] + (*in_row_group_ctr * upsample->rowgroup_height[ci]),
									  upsample->color_buf + ci);
		}
		upsample->next_row_out = 0;
	}

	/* Color-convert and emit rows */

	/* How many we have in the buffer: */
	num_rows = (JDIMENSION) (cinfo->max_v_samp_factor - upsample->next_row_out);
	/* Not more than the distance to the end of the image.  Need this test
	 * in case the image height is not a multiple of max_v_samp_factor:
	 */
	if(num_rows > upsample->rows_to_go)
		num_rows = upsample->rows_to_go;
	/* And not more than what the client can accept: */
	out_rows_avail -= *out_row_ctr;
	if(num_rows > out_rows_avail)
		num_rows = out_rows_avail;

	(*cinfo->cconvert->color_convert) (cinfo, upsample->color_buf,
									   (JDIMENSION) upsample->next_row_out, output_buf + *out_row_ctr, (int)num_rows);

	/* Adjust counts */
	*out_row_ctr += num_rows;
	upsample->rows_to_go -= num_rows;
	upsample->next_row_out += num_rows;
	/* When the buffer is emptied, declare this input row group consumed */
	if(upsample->next_row_out >= cinfo->max_v_samp_factor)
		(*in_row_group_ctr)++;
}


/*
 * These are the routines invoked by sep_upsample to upsample pixel values
 * of a single component.  One row group is processed per call.
 */


/*
 * For full-size components, we just make color_buf[ci] point at the
 * input buffer, and thus avoid copying any data.  Note that this is
 * safe only because sep_upsample doesn't declare the input row group
 * "consumed" until we are done color converting and emitting it.
 */

METHODDEF void
fullsize_upsample(j_decompress_ptr cinfo, jpeg_component_info * compptr, JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
{
	*output_data_ptr = input_data;
}


/*
 * This is a no-op version used for "uninteresting" components.
 * These components will not be referenced by color conversion.
 */

METHODDEF void
noop_upsample(j_decompress_ptr cinfo, jpeg_component_info * compptr, JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
{
	*output_data_ptr = NULL;	/* safety check */
}


/*
 * This version handles any integral sampling ratios.
 * This is not used for typical JPEG files, so it need not be fast.
 * Nor, for that matter, is it particularly accurate: the algorithm is
 * simple replication of the input pixel onto the corresponding output
 * pixels.  The hi-falutin sampling literature refers to this as a
 * "box filter".  A box filter tends to introduce visible artifacts,
 * so if you are actually going to use 3:1 or 4:1 sampling ratios
 * you would be well advised to improve this code.
 */

METHODDEF void
int_upsample(j_decompress_ptr cinfo, jpeg_component_info * compptr, JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
{
	my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
	JSAMPARRAY      output_data = *output_data_ptr;
	register JSAMPROW inptr, outptr;
	register JSAMPLE invalue;
	register int    h;
	JSAMPROW        outend;
	int             h_expand, v_expand;
	int             inrow, outrow;

	h_expand = upsample->h_expand[compptr->component_index];
	v_expand = upsample->v_expand[compptr->component_index];

	inrow = outrow = 0;
	while(outrow < cinfo->max_v_samp_factor)
	{
		/* Generate one output row with proper horizontal expansion */
		inptr = input_data[inrow];
		outptr = output_data[outrow];
		outend = outptr + cinfo->output_width;
		while(outptr < outend)
		{
			invalue = *inptr++;	/* don't need GETJSAMPLE() here */
			for(h = h_expand; h > 0; h--)
			{
				*outptr++ = invalue;
			}
		}
		/* Generate any additional output rows by duplicating the first one */
		if(v_expand > 1)
		{
			jcopy_sample_rows(output_data, outrow, output_data, outrow + 1, v_expand - 1, cinfo->output_width);
		}
		inrow++;
		outrow += v_expand;
	}
}


/*
 * Fast processing for the common case of 2:1 horizontal and 1:1 vertical.
 * It's still a box filter.
 */

METHODDEF void
h2v1_upsample(j_decompress_ptr cinfo, jpeg_component_info * compptr, JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
{
	JSAMPARRAY      output_data = *output_data_ptr;
	register JSAMPROW inptr, outptr;
	register JSAMPLE invalue;
	JSAMPROW        outend;
	int             inrow;

	for(inrow = 0; inrow < cinfo->max_v_samp_factor; inrow++)
	{
		inptr = input_data[inrow];
		outptr = output_data[inrow];
		outend = outptr + cinfo->output_width;
		while(outptr < outend)
		{
			invalue = *inptr++;	/* don't need GETJSAMPLE() here */
			*outptr++ = invalue;
			*outptr++ = invalue;
		}
	}
}


/*
 * Fast processing for the common case of 2:1 horizontal and 2:1 vertical.
 * It's still a box filter.
 */

METHODDEF void
h2v2_upsample(j_decompress_ptr cinfo, jpeg_component_info * compptr, JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
{
	JSAMPARRAY      output_data = *output_data_ptr;
	register JSAMPROW inptr, outptr;
	register JSAMPLE invalue;
	JSAMPROW        outend;
	int             inrow, outrow;

	inrow = outrow = 0;
	while(outrow < cinfo->max_v_samp_factor)
	{
		inptr = input_data[inrow];
		outptr = output_data[outrow];
		outend = outptr + cinfo->output_width;
		while(outptr < outend)
		{
			invalue = *inptr++;	/* don't need GETJSAMPLE() here */
			*outptr++ = invalue;
			*outptr++ = invalue;
		}
		jcopy_sample_rows(output_data, outrow, output_data, outrow + 1, 1, cinfo->output_width);
		inrow++;
		outrow += 2;
	}
}


/*
 * Fancy processing for the common case of 2:1 horizontal and 1:1 vertical.
 *
 * The upsampling algorithm is linear interpolation between pixel centers,
 * also known as a "triangle filter".  This is a good compromise between
 * speed and visual quality.  The centers of the output pixels are 1/4 and 3/4
 * of the way between input pixel centers.
 *
 * A note about the "bias" calculations: when rounding fractional values to
 * integer, we do not want to always round 0.5 up to the next integer.
 * If we did that, we'd introduce a noticeable bias towards larger values.
 * Instead, this code is arranged so that 0.5 will be rounded up or down at
 * alternate pixel locations (a simple ordered dither pattern).
 */

METHODDEF void
h2v1_fancy_upsample(j_decompress_ptr cinfo, jpeg_component_info * compptr, JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
{
	JSAMPARRAY      output_data = *output_data_ptr;
	register JSAMPROW inptr, outptr;
	register int    invalue;
	register JDIMENSION colctr;
	int             inrow;

	for(inrow = 0; inrow < cinfo->max_v_samp_factor; inrow++)
	{
		inptr = input_data[inrow];
		outptr = output_data[inrow];
		/* Special case for first column */
		invalue = GETJSAMPLE(*inptr++);
		*outptr++ = (JSAMPLE) invalue;
		*outptr++ = (JSAMPLE) ((invalue * 3 + GETJSAMPLE(*inptr) + 2) >> 2);

		for(colctr = compptr->downsampled_width - 2; colctr > 0; colctr--)
		{
			/* General case: 3/4 * nearer pixel + 1/4 * further pixel */
			invalue = GETJSAMPLE(*inptr++) * 3;
			*outptr++ = (JSAMPLE) ((invalue + GETJSAMPLE(inptr[-2]) + 1) >> 2);
			*outptr++ = (JSAMPLE) ((invalue + GETJSAMPLE(*inptr) + 2) >> 2);
		}

		/* Special case for last column */
		invalue = GETJSAMPLE(*inptr);
		*outptr++ = (JSAMPLE) ((invalue * 3 + GETJSAMPLE(inptr[-1]) + 1) >> 2);
		*outptr++ = (JSAMPLE) invalue;
	}
}


/*
 * Fancy processing for the common case of 2:1 horizontal and 2:1 vertical.
 * Again a triangle filter; see comments for h2v1 case, above.
 *
 * It is OK for us to reference the adjacent input rows because we demanded
 * context from the main buffer controller (see initialization code).
 */

METHODDEF void
h2v2_fancy_upsample(j_decompress_ptr cinfo, jpeg_component_info * compptr, JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
{
	JSAMPARRAY      output_data = *output_data_ptr;
	register JSAMPROW inptr0, inptr1, outptr;

#if BITS_IN_JSAMPLE == 8
	register int    thiscolsum, lastcolsum, nextcolsum;
#else
	register INT32  thiscolsum, lastcolsum, nextcolsum;
#endif
	register JDIMENSION colctr;
	int             inrow, outrow, v;

	inrow = outrow = 0;
	while(outrow < cinfo->max_v_samp_factor)
	{
		for(v = 0; v < 2; v++)
		{
			/* inptr0 points to nearest input row, inptr1 points to next nearest */
			inptr0 = input_data[inrow];
			if(v == 0)			/* next nearest is row above */
				inptr1 = input_data[inrow - 1];
			else				/* next nearest is row below */
				inptr1 = input_data[inrow + 1];
			outptr = output_data[outrow++];

			/* Special case for first column */
			thiscolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++);
			nextcolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++);
			*outptr++ = (JSAMPLE) ((thiscolsum * 4 + 8) >> 4);
			*outptr++ = (JSAMPLE) ((thiscolsum * 3 + nextcolsum + 7) >> 4);
			lastcolsum = thiscolsum;
			thiscolsum = nextcolsum;

			for(colctr = compptr->downsampled_width - 2; colctr > 0; colctr--)
			{
				/* General case: 3/4 * nearer pixel + 1/4 * further pixel in each */
				/* dimension, thus 9/16, 3/16, 3/16, 1/16 overall */
				nextcolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++);
				*outptr++ = (JSAMPLE) ((thiscolsum * 3 + lastcolsum + 8) >> 4);
				*outptr++ = (JSAMPLE) ((thiscolsum * 3 + nextcolsum + 7) >> 4);
				lastcolsum = thiscolsum;
				thiscolsum = nextcolsum;
			}

			/* Special case for last column */
			*outptr++ = (JSAMPLE) ((thiscolsum * 3 + lastcolsum + 8) >> 4);
			*outptr++ = (JSAMPLE) ((thiscolsum * 4 + 7) >> 4);
		}
		inrow++;
	}
}


/*
 * Module initialization routine for upsampling.
 */

GLOBAL void jinit_upsampler(j_decompress_ptr cinfo)
{
	my_upsample_ptr upsample;
	int             ci;
	jpeg_component_info *compptr;
	boolean         need_buffer, do_fancy;
	int             h_in_group, v_in_group, h_out_group, v_out_group;

	upsample = (my_upsample_ptr) (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, SIZEOF(my_upsampler));
	cinfo->upsample = (struct jpeg_upsampler *)upsample;
	upsample->pub.start_pass = start_pass_upsample;
	upsample->pub.upsample = sep_upsample;
	upsample->pub.need_context_rows = FALSE;	/* until we find out differently */

	if(cinfo->CCIR601_sampling)	/* this isn't supported */
		ERREXIT(cinfo, JERR_CCIR601_NOTIMPL);

	/* jdmainct.c doesn't support context rows when min_DCT_scaled_size = 1,
	 * so don't ask for it.
	 */
	do_fancy = cinfo->do_fancy_upsampling && cinfo->min_DCT_scaled_size > 1;

	/* Verify we can handle the sampling factors, select per-component methods,
	 * and create storage as needed.
	 */
	for(ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; ci++, compptr++)
	{
		/* Compute size of an "input group" after IDCT scaling.  This many samples
		 * are to be converted to max_h_samp_factor * max_v_samp_factor pixels.
		 */
		h_in_group = (compptr->h_samp_factor * compptr->DCT_scaled_size) / cinfo->min_DCT_scaled_size;
		v_in_group = (compptr->v_samp_factor * compptr->DCT_scaled_size) / cinfo->min_DCT_scaled_size;
		h_out_group = cinfo->max_h_samp_factor;
		v_out_group = cinfo->max_v_samp_factor;
		upsample->rowgroup_height[ci] = v_in_group;	/* save for use later */
		need_buffer = TRUE;
		if(!compptr->component_needed)
		{
			/* Don't bother to upsample an uninteresting component. */
			upsample->methods[ci] = noop_upsample;
			need_buffer = FALSE;
		}
		else if(h_in_group == h_out_group && v_in_group == v_out_group)
		{
			/* Fullsize components can be processed without any work. */
			upsample->methods[ci] = fullsize_upsample;
			need_buffer = FALSE;
		}
		else if(h_in_group * 2 == h_out_group && v_in_group == v_out_group)
		{
			/* Special cases for 2h1v upsampling */
			if(do_fancy && compptr->downsampled_width > 2)
				upsample->methods[ci] = h2v1_fancy_upsample;
			else
				upsample->methods[ci] = h2v1_upsample;
		}
		else if(h_in_group * 2 == h_out_group && v_in_group * 2 == v_out_group)
		{
			/* Special cases for 2h2v upsampling */
			if(do_fancy && compptr->downsampled_width > 2)
			{
				upsample->methods[ci] = h2v2_fancy_upsample;
				upsample->pub.need_context_rows = TRUE;
			}
			else
				upsample->methods[ci] = h2v2_upsample;
		}
		else if((h_out_group % h_in_group) == 0 && (v_out_group % v_in_group) == 0)
		{
			/* Generic integral-factors upsampling method */
			upsample->methods[ci] = int_upsample;
			upsample->h_expand[ci] = (UINT8) (h_out_group / h_in_group);
			upsample->v_expand[ci] = (UINT8) (v_out_group / v_in_group);
		}
		else
			ERREXIT(cinfo, JERR_FRACT_SAMPLE_NOTIMPL);
		if(need_buffer)
		{
			upsample->color_buf[ci] = (*cinfo->mem->alloc_sarray)
				((j_common_ptr) cinfo, JPOOL_IMAGE,
				 (JDIMENSION) jround_up((long)cinfo->output_width,
										(long)cinfo->max_h_samp_factor), (JDIMENSION) cinfo->max_v_samp_factor);
		}
	}
}
